The present invention relates to a non-aqueous battery and, in particular, to a non-aqueous second battery whose negative electrode comprises a substance capable of absorbing and releasing lithium ions.
Polypropylene has been used as gasket for the non-aqueous battery. This is because polypropylene does not dissolve or swell in organic solvents used in the non-aqueous battery. However, the non-aqueous battery should have more improved high reliability and accordingly, there have conventionally been developed a variety of techniques such as those listed below. For instance, Japanese Un-examined Patent Publication (hereunder referred to as "J. P. KOKAI") No. Sho 60-35452 discloses that the sealing performance at the sealed portion of the non-aqueous battery can be improved by increasing residual stress at that portion through the use of a polypropylene material having a Rockwell hardness of not less than 95. In addition, J. P. KOKAI Nos. Sho 61-51752 and Sho 63-166140 disclose that the sealing performance can be improved through the use of a crosslinked polypropylene and a highly crystalline polypropylene material, respectively and J. P. KOKAI No. Hei 2-142057 discloses that the sealing performance can be improved through the use of a polypropylene material having a modulus in flexure ranging from 18000 to 30000 kg/cm.sup.2.
Among the foregoing non-aqueous batteries, the non-aqueous second batteries whose negative electrode comprises a substance capable of absorbing and releasing lithium ions are greatly influenced by the external invasive moisture into the batteries and, in particular, the performance thereof is greatly deteriorated. Therefore, the gasket used therein should satisfy more strict requirement for sealing performance. When a polypropylene material having a modulus in flexure of 25000 kg/cm.sup.2 is, for instance, selected as a material for the gasket to increase the stress at the sealing portion, the sealing performance is surely improved and accordingly, the shelf stability thereof is improved. However, the marked improvement in the shelf stability is ensured only when the battery is allowed to stand while it is not in use, but the shelf stability thereof is not always improved when the battery is in use and, in particular, when the battery is, for instance, charged, discharged at a high current or pulse-discharged and used in an atmosphere whose temperature is changed, the degree of deterioration of the battery is rather low when a polypropylene material having a low modulus in flexure is used (this tendency is conspicuous in particular when the negative electrode comprises a lithium-containing transition metal oxide). More specifically, in the conventional techniques, the reduction of the deterioration during using a battery is contrary to the improvement in the shelf stability during storing the battery.